Disposable diaper

ABSTRACT

A disposable diaper includes a liquid-impermeable topsheet, a liquid-permeable backsheet and an absorbent core therebetween. A pair of barrier cuffs which are elastically extendable in a longitudinal direction of the diaper are provided along transversely opposite side flaps of the diaper. Front and rear ends of the barrier cuffs are bonded to the diaper at longitudinally opposite ends thereof. Outer side edges of the barrier cuffs are bonded to outer edges of the flaps and inner side edges of the barrier cuffs are bonded to the flaps along lines defined between the outer side edges and transversely opposite side edges of the core. Each of the barrier cuffs has a dimension between the outer and inner side edges thereof selected to be larger than a dimension of the flap between the outer and inner side edges thereof.

BACKGROUND OF THE INVENTION

This invention relates to a disposable diaper having a high ventilationproperty.

A disposable diaper described in Japanese Utility Model ApplicationDisclosure Gazette (Kokai) No. Sho64-18105 includes a pair ofair-permeable and liquid-resistant barrier flaps formed on a pair oftransversely opposite side flaps so as to elastically extend in alongitudinal direction of the diaper.

Japanese Patent Publication Gazette (Kokai) No. Hei4-55072 discloses amethod for making a backsheet used in a disposable diaper, particularlyto obtain such backsheet made of an air-permeable and liquid-impermeableplastic film.

In these Gazettes, the term “air-permeable and liquid-resistant” and theterm “air-permeable and liquid-impermeable” are synonymously used. Theseknown techniques may be adopted to improve a ventilation property of theforegoing barrier flaps and portions of a diaper backsheet in theproximity of the barrier flaps intended to surround the wearer's legsand thereby to alleviate undesirable stuffiness during use of thediaper.

The diaper proposed by the above-mentioned techniques will necessarilyenlarge a diameter of each aperture formed in the barrier flaps and/orthe backsheet in order to improve the air-permeability in these barrierflaps and/or backsheet. However, such measure may cause the desirableliquid-impermeability required for the barrier flaps and/or thebacksheet. In other words, the conventional techniques have an antimonicrelationship between improvement of the air-permeability and improvementof the liquid-impermeability.

SUMMARY OF THE INVENTION

In view of the problem as has been described above, it is an object ofthe invention to provide a disposable diaper having both a relativelyhigh air-permeability and a relatively high liquid-impermeability.

The present invention provides a disposable diaper, comprising aliquid-permeable topsheet, a liquid-impermeable backsheet and aliquid-absorbent core disposed therebetween so as to form a front waistregion, a rear waist region and a crotch region extending therebetween,and further comprising longitudinally opposite front and rear end flapsand transversely opposite side flaps which are formed by the topsheetand the backsheet extending outward from peripheral edges of theabsorbent core, a pair of barrier cuffs being elastically extendable ina longitudinal direction of the diaper and being bonded, in an extendedcondition, to an inner surface of an associated one of the side flaps.Each of the barrier cuffs has longitudinally opposite front and rearends, and inner and outer side edges extending in parallel to each otherbetween the front and rear ends. The front and rear ends of each of thebarrier cuffs are respectively bonded to the front and rear end flaps.Each of the barrier cuffs has, in the crotch region, the outer side edgebonded to the associated side flap and the inner side edge bonding tothe associated side flap along a line defined between the outer sideedge and an associated edge of the absorbent core. Each of the barriercuffs has, in a transverse cross-sectional view and in the crotchregion: a first wall section formed with a plurality of elastic membersand which first wall section extends inwardly from the outer side edgeof the barrier cuff, an outermost one of the elastic members beingspaced and distinct from the bonding of the outer side edge of thebarrier cuff and the associated side flap, and a second wall sectionintersecting the first wall section inwardly of an innermost one of theelastic members and extending downward to the inner side edge of thebarrier cuff. A dimension of the first wall section in a transversedirection thereof is larger than that of the second wall section in thetransverse direction. The first and second wall sections, together witha portion of the associated side flap defined between the outer andinner side edges, describe a hollow space of a substantially triangularshape, under contraction of the barrier cuff in the longitudinaldirection. Portions of the barrier cuffs and the side flapsparticipating in the formation of the triangular hollow spaces areair-permeable.

According to a preferred embodiment of the invention, elastic membersare bonded, in an extended condition, in the longitudinal direction ofthe diaper, to each of the barrier cuffs in a zone thereof extendingbetween the outer and inner side edges thereof rather adjacent the outerside edge thereof and thereby the barrier cuff is made elasticallystretchable in the longitudinal direction of the diaper.

According to another preferred embodiment of the invention, the barriercuffs and the side flaps are made of an air-permeable andliquid-impermeable material.

According to still another preferred embodiment of the invention, eachof the barrier cuffs has a dimension between the outer and inner sideedges thereof being 1.2˜2.0 times of a dimension of the side flapsimilarly between the outer and inner side edges thereof.

The disposable diaper according to the invention is characterized by aunique arrangement such that leak of body fluids can be double-blockedby the pair of barriers cuffs and the pair of side flaps at least in thecrotch region of the longitudinal three regions, i.e., the front waistregion, the rear waist region and the crotch region extending betweenthe former two regions. This arrangement allows the air-permeability tobe adjusted to relatively high levels in barrier cuff as well as in theside flaps. Each hollow space defined in the crotch region by eachbarrier cuff and the side flap associated with this barrier cuff has itsinner volume which is variable depending on a movement of the diaper.More specifically, vapor-containing air staying within the diaper isexpelled to the exterior of the diaper or dry air is sucked from theexterior into the diaper depending on the movement of the diaper. Inthis manner, a problem of stuffiness from which the wearer would suffercan be effectively solved.

The present invention also provides a disposable diaper comprising aliquid-permeable topsheet, a liquid-impermeable backsheet and aliquid-absorbent core disposed therebetween so as to form a front waistregion, a rear waist region and a crotch region extending therebetween,and further comprising longitudinally opposite front and rear end flapsand transversely opposite side flaps which are formed by both thetopsheet and the backsheet extending outward from peripheral edges ofthe absorbent core, a pair of barrier cuffs being elastically extendablein a longitudinal direction of the diaper and being bonded, in anextended condition, to an inner surface of an associated one of the sideflaps. Each of the barrier cuffs has longitudinally opposite front andrear ends, and inner and outer side edges extending in parallel to eachother between the front and rear ends, the front and rear ends of eachof the barrier cuffs being respectively bonded to the front and rear endflaps. Each of the barrier cuffs has, in the crotch region, the outerside edge bonded to the associated side flap and the inner side edgebonded to the associated side flap in between the outer side edge and anassociated edge o the absorbent core. Each of the barrier cuffs has adimension between the outer and inner side edges selected to be largerthan a dimension of the associated side flap between the outer and innerside edges of each of the barrier cuffs so that a contraction of eachthe barrier cuff in the longitudinal direction of the diaper causes aninner surface of each the barrier cuff to be spaced from an inner surace of the associated side flap at least in the crotch region andthereby forms a hollow space between each the barrier cuff and theassociated side flap. Portions of the barrier cuffs and the associatedside flaps participating in the formation of the hollow spaces areair-permeable. The outer side edge of each of the barrier cuffs, in thecrotch region, is directly bonded to the topsheet in the associated sideflap along a line where the topsheet and the backsheet are bondedtogether.

In accordance with an aspect of the present invention, the topsheetextends to the outer side edge of the barrier cuff.

In accordance with another aspect of the present invention, theextension stress of the innermost elastic member is less than that ofthe outermost elastic member.

In accordance with a further aspect of the present invention, theextension stress of the middle elastic member(s) is less that that ofthe innermost elastic member.

In accordance with yet another aspect of the present invention, thepermeability of the backsheet in the hollow space is higher than in theremainder thereof.

Still other objects and advantages of the present invention will becomereadily apparent to those skilled in the art from the following detaileddescription, wherein the preferred embodiments of the invention areshown and described, simply by way of illustration of the best modecontemplated of carrying out the invention. As will be realized, theinvention is capable of other and different embodiments, and its severaldetails are capable of modifications in various obvious respects, allwithout departing from the invention. Accordingly, the drawings anddescription thereof are to be regarded as illustrative in nature, andnot as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an embodiment of a disposablediaper according to the invention as partially broken away;

FIG. 2 is a sectional view taken along a line II—II in FIG. 1;

FIG. 3 is a sectional view taken along a line III—III in FIG. 1; and

FIG. 4 is a view similar to FIG. 2 showing an alternative embodiment ofthe diaper according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Details of a disposable diaper provided according to the invention willbe more fully understood from the following description with referenceto the accompanying drawings.

Disposable diaper 1 shown by FIG. 1 in a perspective view as partiallybroken away comprises a liquid-permeable topsheet 2, aliquid-impermeable backsheet 3 and a liquid-absorbent core 4 disposedbetween these two sheets 2, 3. These sheets 2, 3 and absorbent core 4forms a front waist region 6, a rear waist region 7 and a crotch region8 longitudinally extending between these two regions 6, 7. The absorbentcore 4 is in a shape of rectangle or hourglass which is relativelylarger longitudinally of the diaper 1. Portions of the topsheet 2 andthe backsheet 3 extending outward beyond peripheral edges of theabsorbent core 4 are placed upon each other and bonded together by meansof hot melt adhesive (not shown) so as to form longitudinally oppositefront and rear end flaps 11, 12 and transversely opposite side flaps 13.In the front and rear waist regions 6, 7, each of the side flaps 13extend outward to form front and rear wings 13A, 13B, respectively. Eachof the side flaps 13 is formed on an inner surface thereof with abarrier cuff 14 extending along the crotch region 8 and partially intothe front and rear waist regions 6, 7. The barrier cuff 14 is providedwith a plurality of elastic members 29 extending longitudinally thereof.The front and rear end flaps 11, 12 are provided between the topsheet 2and the backsheet 3 with elastic members 16, 17 extendingcircumferentially of the respective waist regions 6, 7. The elasticmembers 16, 17 are secured, in an extended condition, to an innersurface of at least one of the topsheet 2 and the backsheet 3. A pair oftape fasteners 16 a are attached to the respective wings 13B of the rearwaist region 7 in the vicinity of side edges thereof.

FIG. 2 is a sectional view taken along a line II—II in FIG. 1. Thebarrier cuff 14 is made of an air-permeable sheet and comprises, as seentransversely of the diaper 1, an outer side edge 23 bonded to an innersurface of the side flap 13 along an outer edge 20 thereof by means ofhot melt adhesive 22 a and an inner side edge 26 bonded to an innersurface of the side flap 13 with adhesive 22 b along an intermediatezone between the outer side edge 23 and a side edge 24 of the absorbentcore 4. The barrier cuff 14 further comprises longitudinally oppositefront and rear ends 27, 28 (See FIG. 1) bonded to the respective endflaps 11, 12 of the front and rear waist regions 6, 7. The barrier cuffplaced upon the side flap 13 has a plurality of elastic members 29secured, in an extended condition in the longitudinal direction, to theinner surface of the side flap 13 by means of hot melt adhesive (notshown).

The barrier cuff 14 has a transverse dimension A between the outer andinner side edges 23, 26 and the side flap 13 has a transverse dimensionB similarly between the two side edges 23, 26. The dimension A ispreferably 1.2˜2.0 times, more preferably 1.3˜1.7 times of the dimensionB which is, in turn, preferably in a range of 15˜90 mm. Referring toFIG. 2, the elastic members 29 of the barrier cuff 14 are designated byreference numerals 29A˜29E. Of the elastic members 29A˜29E, theoutermost elastic member 29A longitudinally extending adjacent the outerside edge 23 has the highest extension stress and the innermost elasticmember 29E longitudinally extending between the outer side edge 23 andthe inner side edge 26 has an extension stress equal to or less than theextension stress of the elastic member 29A. The elastic members 29B˜29Dinterposed between the two elastic members 29A, 29E respectively have anextension stress equal to or less than the extension stress of theelastic member 29E. The number of the elastic members 29B,˜29D to beinterposed between the elastic members 29A, 29E is not limited to thenumber used in the embodiment of FIG. 2 and may be selectively increasedor decreased without departing from the scope of the invention. When thediaper 1 is inwardly curved along a longitudinal axis thereof with thetopsheet inside as shown in FIG. 1, contraction of the elastic members29 causes the inner surface of the barrier cuff 14 to be moved away fromthe inner surface of the side flap 13. Consequently, the barrier cuff 14cooperates with the side flap 13 to form a hollow space 31. In a stateof the barrier cuff 14 having thus formed the hollow space 31, a wallsection of the barrier cuff 14 defined between the elastic member 29Aand the elastic member 29E is substantially flat and a wall section C ofthe barrier cuff 14 defined between the elastic member 29E and the innerside edge 26 is forced by the absorbent core 4 to extends downwardbecause the absorbent core 4 is lowered as the diaper 1 is curvedinwardly. The side flap 13 extends obliquely between the outer side edge23 and the inner side edge 26 of the barrier cuff 14, as seen in FIG. 2.

The barrier cuff 14 serving as an important component of the hollowspace 31 comprises the air-permeable sheet as previously mentioned. Onthe other hand, the backsheet 3 is formed with a plurality ofair-permeable apertures 32 and the topsheet 2 placed upon the backsheet3 is also air-permeable and liquid-permeable. Thus, a portion of theside flap 13 serving as another component of the hollow space 31 andcomprising the topsheet 2 and the backsheet 3 is also air-permeable.Accordingly, the substantially entire peripheral wall defining thehollow space 31 is air-permeable.

FIG. 3 is a sectional view taken along a line III—III in FIG. 1. Asshown, the hollow space 31 is collapsed in the vicinity of thelongitudinal ends of the front and rear waist regions 6, 7,respectively. In the vicinity of the longitudinal ends of the front andrear region 6, 7, the barrier cuff 14 is bonded to the upper surface ofthe topsheet 2 and, at the same time, layers of the barrier cuff 14folded one upon another are bonded together by means of hot meltadhesive 22 c.

With the diaper 1 of such construction being put on a wearer, therelatively flat wall of the barrier cuff 14 extending between theelastic member 29A and the elastic member 29E is normally placed againsta crotch zone or around the legs of the wearer. In this state, the wallsection C and the side flap 13 of the barrier cuff 14 extend downward soas to cooperate with the relatively flat wall to define the hollow space31. Depending on a posture taken by the wearer, the absorbent core 4 maymove upward into close contact with the wearer's crotch zone, collapsingthe hollow space 31 and thereby decreasing its inner volume. However,the hollow space 31 restores again to its full inner volume shown inFIG. 2 as the absorbent core 4 downward moves away from the wearer'scrotch zone. As the inner volume of the hollow space 31 decreases,vapor-containing air staying within the hollow space 31 as well asstuffy air in the diaper 1 is expelled to the exterior through theair-permeable barrier cuff 14 and the air-permeable side flap 13. On thecontrary, as the inner volume of the hollow space 31 increases, externaldry air is sucked through the barrier cuff 14 and the side flap 13 tothe interior of the diaper 1.

With such diaper 1, an amount of body fluids flowing sideways over thecrotch region 8 is blocked by the barrier cuff 14. Even if the amount ofbody fluids flowing sideways has partially penetrated the barrier cuff14 to the hollow space 31, such amount of body fluid is then preventedby the side flap 13 from further flowing sideways to the exterior of thediaper 1. In this manner, the amount of body fluids which otherwisemight leak sideways over the crotch region 8 can be double-blocked andthis feature allows air-permeability of the barrier cuff 14 as well asof the side flap 13 to be adjusted to a relatively high value.

FIG. 4 is a view similar to FIG. 2 showing an alternative embodiment ofthe invention. This specific embodiment of the diaper 1 is similar tothat of FIG. 2 except as to a configuration of its side flaps 13. Theside flap 13 shown in FIG. 4 comprises the topsheet 2 largely extendingbeyond the side edge 24 of the absorbent core 24, the backsheet 3slightly extending beyond the side edge 24, and an extension sheet 36bonded to an outer end of the extended backsheet 3 by means of hot meltadhesive 22 d. The topsheet 2, backsheet 3 and extension sheet 36 areplaced one upon another and/or overlapped one by another and bondedtogether along predetermined zones utilizing lines of hot melt adhesive22 e, 22 f, 22 g. Each extension sheet 36 extends not only along theside edge of the crotch region 8 but also along respective side edges ofthe front and rear waist regions 6, 7 to their longitudinal ends.Preferably, the extension sheet 36 has an air-permeability higher thanthat of the backsheet 3.

To exploit the invention, a liquid-permeable nonwoven fabric or aliquid-permeable apertured plastic sheet may be employed as material forthe topsheet 2. Such nonwoven fabric preferably has a basis weight of10˜50 g/m². The backsheet 3 is made of a plastic sheet, more preferablyof air-permeable and liquid-permeable plastic sheet. The portion of thebacksheet 3 participating in formation of the hollow space 31 may beformed with a plurality of apertures 32 each having a diameter of 0.1˜2mm at a total aperture area ratio of 2˜10% with respect to an entirearea of the aforesaid portion in order to improve its air-permeability.The air-permeable sheet as the important component of the barrier cuff14 may be made of an air-permeable nonwoven fabric having a basis weightof 10˜100 g/m². The barrier cuff 14 may be double-layered as in theembodiments shown, but the barrier cuff 14 may be realized also in theform of a single-layered sheet. According to the embodiments shown, theportions of the topsheet 2 and the backsheet 3 participating information of the hollow space 31 are placed upon each other. Sucharrangement ensures that, even if the apertures 32 of the backsheet 3are of relatively large diameter, body fluids can be effectivelyprevented from leaking through the apertures 32. If it is unnecessary toprovide the backsheet 3 with those apertures 32 for improvement of itsair-permeability, the topsheet 2 may be bonded to the inner side edge 26of the barrier cuff 14 and terminated at this bonding line withoutfurther extending into the hollow space 31. Nonwoven fabrics employed asmaterial for the topsheet 2, the backsheet 3 and the extension sheet 36may be locally treated to provide them with hydrophilic or hydrophobicnature, so far as they have zones requiring such treatment.

What is claimed is:
 1. A disposable diaper, comprising aliquid-permeable topsheet, a liquid-impermeable backsheet and aliquid-absorbent core disposed therebetween so as to form a front waistregion, a rear waist region and a crotch region extending therebetween,and further comprising longitudinally opposite front and rear end flapsand transversely opposite side flaps which are formed by said topsheetand said backsheet extending outward from peripheral edges of saidabsorbent core, a pair of barrier cuffs being elastically extendable ina longitudinal direction of said diaper and being bonded, in an extendedcondition, to an inner surface of an associated one of said side flaps;each of said barrier cuffs having longitudinally opposite front and rearends, and inner and outer side edges extending in parallel to each otherbetween said front and rear ends; said front and rear ends of each ofsaid barrier cuffs being respectively bonded to said front and rear endflaps; each of said barrier cuffs has, in said crotch region, said outerside edge bonded to said associated side flap and said inner side edgebonded to said associated side flap along a line defined between saidouter side edge and an associated edge of said absorbent core; each ofsaid barrier cuffs has, in a transverse cross-sectional view and in thecrotch region, a first wall section formed with a plurality of elasticmembers and which first wall section extends inwardly from the outerside edge of said barrier cuff, an outermost one of said elastic membersbeing spaced and distinct from said bonding of the outer side edge ofsaid barrier cuff and the associated side flap, and a second wallsection intersecting the first wall section inwardly of an innermost oneof said elastic members and extending downward to the inner side edge ofsaid barrier cuff, wherein a dimension of said first wall section in atransverse direction thereof is larger than that of said second wallsection in said transverse direction, and said first and second wallsections, together with a portion of said associated side flap definedbetween said outer and inner side edges, describe a hollow space of asubstantially triangular shape, under contraction of said barrier cuffin the longitudinal direction; and portions of said barrier cuffs andsaid side flaps participating in the formation of said triangular hollowspaces are air-permeable; wherein a sum of the transversely extendingdimensions of said first and second wall sections is greater than adimension of a portion of the associated side flap defined between theinner and outer edges of the associated barrier cuff; and said pluralityof elastic members include at least three elastic members, the innermostelastic member has an extension stress less than an extension stress ofthe outermost elastic member, and an extension stress of the elasticmember or members disposed between the innermost and outermost elasticmembers is less than the extension stress of the innermost elasticmember.